Variations on the Trainer Theme: Pilatus PC-21

The shoreline of the Lake of Luzern, surrounded by the mountains of the Swiss Alps, is not perhaps where you would expect to find an airfield and associated aircraft factory; however, flat terrain is at a premium in Switzerland, and this particular piece of real estate on the outskirts of the town of Stans, hard up against a ridge of Mount Pilatus, is Buochs Airport, the home of Pilatus Aircraft. MS&T’s Dim Jones recently visited to explore the PC-21.

Pilatus Aircraft was established on 10th December 1939 by the armament company Oerlikon-Bührle for the maintenance and repair of Swiss Air Force aircraft. The location was to be well removed from the German border and, indeed, the facility was originally to be built inside the mountain for protection. Buochs was a Swiss Air Force base until 2003, latterly operating Mirage IIIRS and F-5E, which were accommodated within rock caverns. Since then the military facilities have been on a ‘care and maintenance’ basis, with a reactivation capability last exercised in 2014 for an exercise involving F-5E and F/A-18 aircraft.

Between 1940 and 1958, alongside their repair and maintenance duties, Pilatus produced a number of aircraft designs, designated P-1 to P-5, some of which were project only, and others no more than a single prototype. The 1945 P-2, however, was a two-seat trainer for the Swiss Air Force, and its 1953 successor, the P-3, was sold to the Brazilian Navy. In 1966, a turboprop version of the P-3, designated PC-7, first flew, but the prototype crashed, and production was delayed until the 1970s. Meanwhile, the company was also developing a Short Landing and Take-off (STOL) light transport, and 1959 saw the first flight of the legendary PC-6 Pilatus Porter, and 1999 its equally successful successor, the PC-12, of which more than 1600 have been sold worldwide. Feedback from PC-12 customers, who wanted increased range and speed without sacrificing short field performance, led to the development of the twin-jet PC-24, the first of which was delivered to a US customer in January of this year.

The company itself has continuously expanded and has produced more than 3700 aircraft over the years. 100% Swiss-owned, and now with a workforce of over 2000 at Stans, Pilatus is one of the largest employers in Central Switzerland and provides training for about 120 apprentices in 13 different professions. There are also independent subsidiary companies in the US and Australia. The company’s commitment to the environment is symbolised by the splendid timber framing of the newest hangars.

Returning to the theme of military aircraft, the revived PC-7 basic trainer, introduced in 1978, has been sold to more than 20 air forces and the 500 or so aircraft, many still in service, have flown more than one million hours.

The PC-21 Aircraft Systems Trainer (AST), an interactive desktop systems and procedures trainer, can be integrated with a Hands On Throttle-And-Stick (HOTAS).All images: Pilatus Aircraft

Its successor, the PC-9, first flew in 1985 and, since then, more than 250 airframes have been produced for the Swiss Air Force, and those of Saudi Arabia, Thailand and Australia.

Development of a next-generation trainer began in 1999, and the PC-21 first flew in July 2002. The latest version retains the performance of the original, powered by a P&W Canada PT6A-68B turboprop, delivering 1600SHP. It is a low-wing monoplane with a stepped tandem seating arrangement, giving the rear-seat occupant good forward vision, although – for aerodynamic design reasons – not as good as the ‘stadium seating’ allowed by jet trainers such as the Hawk, M-346, T-50 and Boeing T-X. It is similar in configuration to the T-6A Texan 2 – indeed, both are developments of the PC-9 – and the Embraer Super Tucano.

‘The 21st Century Trainer’

The PC-21 is equipped with underwing hardpoints, which allow the carriage of external fuel tanks and smoke pods (for aerial displays) but, unlike Embraer or Beechcraft, Pilatus does not support any of the other external stores which would be required to use the aircraft in a light attack role. A pressurised, air-conditioned cabin, on board oxygen generator system (OBOGS), autopilot, anti-G, Martin Baker zero-zero ejection seats, hydraulically assisted aileron and spoiler giving roll rates around the 200o/sec mark, auto-yaw compensation, and a +8/-4G envelope complete the specification. Engine management is simplified with power scheduling as a function of airspeed, electronic fuel scheduling, propeller control and protection, mechanical back-up and auto-start.

It is the cockpit and avionics of the PC-21, however, which transform it into what Pilatus call ‘the 21st-century trainer’ and, more fundamentally, transform its potential utility from just a basic (Phase 2/3) platform to something much more versatile. The cockpit layout embodies: three 6x8 full-colour reconfigurable night vision goggle (NVG)-compatible multi-function displays (MFDs); customised Hands On Throttle-And-Stick (HOTAS); and a head-up display (HUD), with display adaptable to suit the end-user – the rear cockpit lacks the HUD, but has a repeater.

The embedded simulation and training suite comprises tactical navigation and moving map, stores management, simulated air-to-air and air-to-ground radar and electronic countermeasures (ECM), radar target simulation through data link, air-to-air and air-to-ground weapons parameters simulation, and a no-drop bomb-scoring system (NDBS).

The tactical navigation display shows tactical routes with time on target, and intelligence information, such as ground-based air defence (GBAD) threats, inserted through the Mission Planning and Debriefing System (MPDS). The simulated radar can replicate either APG-65 or APG-68, with air combat modes, and can show either synthetic or real targets, the latter through data link. The electronic warfare (EW) suite includes simulated radar warning receiver (RWR), chaff and flares.

Weapons engagement parameters are displayed for generic short-range infrared (IR), medium-range active radar-guided missiles, and lead-computed or continuously computed gunsight, thus allowing training from beyond visual range (BVR) to close combat. The synthetic air-to-ground radar displays ground-mapping, expanded and Doppler Beam Shift (DBS) modes in various ranges, and with a freeze/cursor slew/unfreeze facility and automatic antenna elevation. Air-to-ground simulated bomb delivery is either Continuously Computed Release Point (CCRP) or Impact Point (CCIP) against pre-designated ground targets, or Dive Toss (DTOS) or CCIP rockets against non-designated targets. The PC-21 provides a real-time and post-flight debrief scoring system for A-A and A-G missiles, guns and bombs. There is, as yet, no emulated sensor pod, but this could be developed if required by a customer.

The integrated mission computer is open architecture, thus allowing software customisation to suit customer requirements. Lastly, the rear cockpit displays can either mirror those of the front, or be split-cockpit, thus allowing the instructor to monitor any systems which the student does not have selected, or to insert data to which the student is not privy, such as threats or simulated targets.

The aircraft’s mission data recorder records all video, audio and mission data information for later use by the MPDS that, as the name implies, comprises mission planning and debriefing elements. Data is transferred from planning system to aircraft, and from aircraft to debriefing via a Pilot Memory Module (PMM). Loadable data includes raster maps, satellite imagery, vector maps, terrain data, terminal charts, images, and a Digital Aeronautical Information File (DAFIF), a comprehensive database of aeronautical data. Route data can include points of interest (POI), surface-to-air missile (SAM) envelopes and bullseyes. A-A and A-G profiles can also be stored. The debrief system can show the outside world with HUD symbology overlaid and audio comms, an external 3-D view of up to four aircraft, and all cockpit displays.

Ground-Based Training Tools

Pilatus can provide a full range of ground-based training systems for the PC-21, from physical training aids and computer-based training (CBT) to a Full Mission Simulator (FMS) with 330o horizontal and above 100o vertical field-of-view dome visual. All images: Pilatus Aircraft

Pilatus can provide its customers with a full range of ground-based training systems, including: training documents, in both hard copy and electronic format; physical training aids, such as wall-boards, cockpit mock-ups and ‘fighting sticks’; and computer-based training (CBT), to include computer-aided instruction (CAI). The full suite of available synthetic training devices comprises: an Aircraft Systems Trainer (AST), which is an interactive desktop systems and procedures trainer, and can be integrated with a HOTAS stick and throttle for practice in their use; an Integrated Procedures Trainer (IPT); a Flight Training Device (FTD), with limited visual; and a Full Mission Simulator (FMS) with a dome visual.

I had the opportunity to fly both the FTD and the FMS and found them extremely effective. The FTDs and FMSs can have a variety of layouts and visual system field-of-view (FOV), the most advanced being a dome with 330o horizontal and above 100o vertical FOV. The simulators for the various customers are built by Pilatus, who retain ultimate responsibility for delivery, but elements of the work are outsourced to companies such as Airbus, Lockheed Martin and CAE, according to the customer’s wishes. The company also trains cadres of instructors and maintainers from customer air forces at Stans, and could provide in-country training, if required.

A Reflection of Versatility

The French Armée de l'Air will replace Phase 2 and 3 Alphajets with PC-21s. The PC-21 is thus far in service with eight air forces. All images: Pilatus Aircraft

It is often said that, for aircraft up to 3rd-generation, the pilot workload was 75% flying the aircraft and 25% operating the systems, and that, in 5th-generation, these percentages are at least reversed. There is no doubt that the modern pilot is more a mission manager, data disseminator and decision maker than aircraft operator; there is also little doubt that avionically advanced training aircraft such as the PC-21 can provide a student pilot with a significant proportion of the challenges and skills he or she will need on a modern front line aircraft, thus allowing download of training tasks from the front-line, and improved performance, born of familiarity, when arriving at the operational conversion unit (OCU). All modern training aircraft are, to a greater or lesser degree, so equipped.

There is also little doubt that a turboprop aircraft is cheaper to operate than a jet – although Leonardo hope to challenge this premise with the M-345 High Efficiency Trainer (HET). A smaller number of aircraft types in the training pipeline also saves money through reduced logistic support and type training. However, while the effectiveness of advanced turboprop aircraft in basic and advanced flying training is undisputed, their utility at the edges of the training spectrum is not, and the debate continues.

The principal reservation many air forces have is on performance, and particularly on speed. The PC-21 handles much like a fighter, and all modern combat aircraft are easy to fly anyway. However, will a low-level cruise speed of 300 - 325 kts and a maximum operating speed of 370KIAS/M0.72 adequately prepare a student for the F-35? Is a G-limit of +8 adequate if it cannot be sustained?

The PC-21 is thus far in service with eight air forces and, as may be expected, the roles in which it is used vary markedly, sometimes influenced, it must be said, by the existence of legacy platforms for other phases of training. These differences in themselves are a reflection of the versatility of the aircraft; furthermore, it may well be that, having taken delivery of PC-21, the customer’s view of what it can do and where it fits in to their training pipeline may well change.

The Swiss Air Force use PC-7 for Phase 2 training, and PC-21 for Phases 3 and 4 (culminating in 2v2 BVR radar intercepts); students then proceed direct to the F/A-18. The Royal Saudi Air Force (RSAF) purchased PC-21 as a straight replacement for PC-9 for Phase 2/3 training, and the Hawk AJT for Phase 4, but it may be that they can now download some training from Hawk to PC-21. Similarly, Australia purchased PC-21 as a PC-9 replacement for Phases 2 and 3 and will continue to use an updated Hawk 127 for Phase 4. Singapore uses PC-21 for Phases 2 and 3, and M-346 for Phase 4. Qatar, having recently purchased Super Mushshak for screening and air experience, will use the PC-21 for basic and advanced training, a significant vote of confidence since their fighter front line will eventually comprise Mirage 200-5, Rafale, Typhoon and F-15. The UAE intended PC-21 as a PC-7 replacement, with Hawk 102 as the Fighter Lead-In Training (FLIT) aircraft; however, they are now using PC-21 as the Phase 4 aircraft for those students destined for F-16 (similar configuration), and Hawk for those destined for Mirage 2000. France will replace Phase 2 and 3 Alphajets with PC-21 and intend to download training from the few upgraded FLIT Alphajets in order to maximise airframe life. The purchase of a new FLIT aircraft, as yet unconfirmed, is made more likely by the French requirement for live weaponry during Phase 4. Lastly, the Royal Jordanian Air Force ordered PC-9s for Phase 2 and 3, expecting to use Hawk 63s gifted from the UAE for FLIT; however, they have recently changed the order to PC-21 and taken the Hawks out of service on cost of operation grounds – future students will start on the Grob 120TP, progress to the PC-21, thence direct to the F-16. Finally, QinetiQ, who run the Empire Test Pilot School (ETPS) at Boscombe Down, UK have purchased two PC-21s as project aircraft replacements for the Hawk T1 on their new course.

So, there are as many variations on a theme as there are current customers. The debate will doubtless continue and may focus on the early part of the pipeline as well as the end. Is it cost-effective to be using a sophisticated aircraft like the PC-21 for Phase 2 Basic Training? If the FLIT platform is less avionically sophisticated than the Phase 3 aircraft, will this constitute ‘negative training’ and, since tasks cannot be downloaded from the front-line OCUs to such an aircraft, can they be downloaded to Phase 3?

A future RAF pilot will graduate from the Grob 120TP to the T-6 Texan 2 (apparently fairly similar in specification to the PC-21), but the FLIT aircraft is the equally well-equipped Hawk T2, while the RAAF’s upgraded Hawk 127s are virtually identical to the Mk128 (T2), as is the Mk165 for the RSAF. Singapore has the equally capable M346, but the same cannot be said for owners of legacy aircraft such as Alphajet and earlier marks of Hawk. The requirements for the USAF T-38 replacement (T-X), the successful contender for which will shortly be announced, made plain at an early stage that a high-performance and avionically sophisticated jet aircraft would be required, and subsequently that only the most modern would meet the agility and sustained G thresholds. Meanwhile, paradoxically, the US Navy soldiers on (if that is not oxymoronic), for now at least, with the T-45 Goshawk, a much-modified carrier-capable version of the Hawk T1.

The conundrum can, perhaps, be encapsulated in two axioms, the first Gallic: “À chacun son gout (To each his own taste)” and the second prosaically Anglo-Saxon or, more specifically, Cockney: “You pays yer money, you takes yer choice”

Originally published in Issue 3, 2018 MS&T.